Extendible stent apparatus

ABSTRACT

The present invention concerns novel stent apparatuses for use in treating lesions at or near the bifurcation point in bifurcated cardiac, coronary, renal, peripheral vascular, gastrointestinal, pulmonary, urinary and neurovascular vessels and brain vessels. More particularly, the invention concerns a stent apparatus with at least one side opening which may further comprise an extendable stent portion laterally extending from the side opening and at least partly in registry with the wall of the side opening. Devices constructed in accordance with the invention include, singularly or in combination, a main expandable stent comprising at least one substantially circular side opening located between its proximal and distal end openings, which side opening may further comprise an expandable portion extending radially outward from the edges of the side opening; and a branch stent comprising proximal and distal end openings and which may further comprise a contacting portion at its proximal end, and which may optionally be constructed to form either a perpendicular branch or a non-perpendicular branch when inserted through a side opening of the main stent. The stents of the invention are marked with, or at least partially constructed of, a material which is imageable during intraluminal catheterization techniques, most preferably but not limited to ultrasound and x-ray.

RELATED APPLICATIONS

This Application is a continuation-in-part of U.S. patent applicationSer. No. 08/744,002, filed on Nov. 4, 1996 and now abandoned.

BACKGROUND

A type of endoprosthesis device, commonly referred to as a stent, may beplaced or implanted within a vein, artery or other tubular body organfor treating occlusions, stenoses, or aneurysms of a vessel byreinforcing the wall of the vessel or by expanding the vessel. Stentshave been used to treat dissections in blood vessel walls caused byballoon angioplasty of the coronary arteries as well as peripheralarteries and to improve angioplasty results by preventing elastic recoiland remodeling of the vessel wall. Two randomized multicenter trialshave recently shown a lower restenosis rate in stent treated coronaryarteries compared with balloon angioplasty alone (Serruys, P W et. al.New England Journal of Medicine 331: 489-495, 1994, Fischman, D L et.al. New England Journal of Medicine 331: 496-501, 1994). Stents havebeen successfully implanted in the urinary tract, the bile duct, theesophagus and the tracheo-bronchial tree to reinforce those body organs,as well as implanted into the neurovascular, peripheral vascular,coronary, cardiac, and renal systems, among others. The term “stent” asused in this application is a device which is intraluminally implantedwithin bodily vessels to reinforce collapsing, dissected, partiallyoccluded, weakened, diseased or abnormally dilated or small segments ofa vessel wall.

One of the drawbacks of conventional stents is that they are generallyproduced in a straight tubular configuration. The use of such stents totreat diseased vessels at or near a bifurcation (branch point) of avessel may create a risk of compromising the degree of patency of theprimary vessel and/or its branches, or the bifurcation point and alsolimits the ability to insert a second stent into the side branch if theresult of treatment of the primary, or main, vessel is suboptimal.Suboptimal results may occur as a result of several mechanisms, such asdisplacing diseased tissue, plaque shifting, vessel spasm, dissectionwith or without intimal flaps, thrombosis, and embolism.

The risk of branch compromise is increased generally in two anatomicalsituations. First, a side branch may be compromised when there is astenosis in the origin of the side branch. Second, when there is aneccentric lesion at the bifurcation site, asymmetric expansion can causeeither plaque shifting or dissection at the side branch origin. Thereare reports of attempts to solve this problem by inserting a ballooninto the side branch through the struts of a stent deployed in the mainbranch spanning the bifurcation point; however, this technique carriesthe risk of balloon entrapment and other major complications (Nakamura,S. et al., Catheterization and Cardiovascular Diagnosis 34: 353-361(1995)). Moreover, adequate dilation of the side branch is limited byelastic recoil of the origin of the side branch. In addition, insertionof a traditional stent into a main vessel spanning a the bifurcationpoint may pose a limitation to blood flow and access to the side branchvessel. The term “stent jail” is often used to describe this concept. Inthis regard, the tubular slotted hinged design of the Palmaz-Schatzintracoronary stent, in particular, is felt to be unfavorable forlesions with a large side branch and is generally believed to pose ahigher risk of side branch vessel entrapment where the stent prevents orlimits access to the side branch. Id.

One common procedure for intraluminally implanting a stent is to firstopen the relevant region of the vessel with a balloon catheter and thenplace the stent in a position that bridges the treated portion of thevessel in order to prevent elastic recoil and restenosis of thatsegment. The angioplasty of the bifurcation lesion has traditionallybeen performed using the “kissing” balloon technique where twoguidewires and two balloons are inserted, one into the main branch andthe other into the side branch. Stent placement in this situationrequires the removal of the guidewire from the side branch andreinsertion through the stent struts, followed by the insertion of aballoon through the struts of the stent along the guidewire. The firstremoval of the guidewire poses the risk of occlusion of the side branchduring the deployment of the stent in the main branch.

Prior art patents refer to the construction and design of both the stentas well as the apparatus for positioning the stent within the vessel.One representative patent to Chaudhury, U.S. Pat. No. 4,140,126,discloses a technique for positioning an elongated cylindrical stent ata region of an aneurysm to avoid catastrophic failure of the bloodvessel wall. The '126 patent discloses a cylinder that expands to itsimplanted configuration after insertion with the aid of a catheter.Dotter, U.S. Pat. No. 4,503,569, discloses a spring stent which expandsto an implanted configuration with a change in temperature. The springstent is implanted in a coiled orientation and is then heated to causethe spring to expand. Palmaz, U.S. Pat. No. 4,733,665, discloses anumber of stent configurations for implantation with the aid of acatheter. The catheter includes a mechanism for mounting and retaining astent, preferably on an inflatable portion of the catheter. The stentsare implanted while imaged on a monitor. Once the stent is properlypositioned, the catheter is expanded and the stent separated from thecatheter body. The catheter can then be withdrawn from the subject,leaving the stent in place within the blood vessel. Palmaz, U.S. Pat.No. 4,739,762, discloses an expandable intraluminal graft. Schjeldahlet. al., U.S. Pat. No. 4,413,989, discloses a variety of ballooncatheter constructions. Maginot, U.S. Pat. No. 5,456,712 and Maginot,U.S. Pat No. 5,304,220 disclose a graft and stent assembly and a methodof implantation where a stent is used to reinforce a graft that issurgically inserted into a blood vessel in order to bypass an occlusion.However, none of these patents relate to stents which are structurallyadapted for the treatment of bifurcation lesions, or disclose abifurcating stent apparatus.

Taheri , U.S. Pat. No. 4,872,874, Piplani et. al., U.S. Pat. No.5,489,295, and Marin et al., U.S. Pat. No. 5,507,769, disclosebifurcating graft material which may be implanted using stents asanchors for the graft. However, bifurcated stents are not taught ordisclosed, and the purpose of the stent as used in these inventions issimply to anchor the graft into the vessel wall. It does not reinforcethe vessel wall, treat a lesion, or prevent restenosis afterangioplasty.

MacGregor, U.S. Pat. No. 4,994,071, discloses a hinged bifurcatingstent. In the 071' patent, in contrast to the present invention, thereis a main stent with two additional stents attached at one end of themain stent, creating a single unit with a trunk attached at an end totwo smaller stents. The two additional stents are permanently attachedto the end of the trunk (and not the side, as in the present invention)and cannot be removed from the main stent. Thus, this invention may notbe used to treat only one branch of a bifurcated vessel, is notappropriate for use when the branch vessel extends laterally from theside of a main vessel (as opposed to an end of a main vessel), and doesnot cover the origin of a bifurcated vessel or bifurcation lesion. Inaddition, studies with hinge-containing stents have shown that there isa high incidence of restenosis (tissue growth) at the hinge point thatmay cause narrowing or total occlusion of the vessel and thus compromiseblood flow. Furthermore, this design has a relatively large size ascompared to the present invention, which makes insertion into manysmaller vessels difficult and poses a greatly increased risk ofcomplications. Also, by having the two additional smaller stentsconnected to an end of the trunk stent, tracking into a wide-anglelateral side branch may be difficult and may carry the risk ofdissection of the vessel wall. Furthermore, once the device of the '071patent is implanted, it is impossible to exchange a branch stent shouldthe need for a different stent size or repair of a branch stent arise.

Marcade, U.S. Pat. No. 5,676,696, discloses a bifurcated graft assemblyused for repairing abdominal aortic aneurysms, comprising a series ofinterlocked tubes, one of which comprises a fixed angle singlebifurcated graft assembly. In contrast to the present invention, Marcadediscloses a graft, not a stent, which may not be used to treat only onevessel of a bifurcation (leaving the untreated vessel free from allobstructions). In addition, and in contrast to the present invention,the one-piece bifurcated graft portion of Marcade is uniform in size andfixed in angle, and may not be used in a vessel bifurcation where thebranch and the main vessels differ greatly in size. Also, the fixedangle will not provide as exact a fit as the variably-angled brancheddouble-stent of the invention.

U.S. Pat. No. 5,653,743 to Martin discloses a bifurcated graft assemblyfor use in the hypogastric and iliac arteries. In addition to teachinggrafts (which are used to replace diseased vessel material) and notstents (which, as used herein, reinforce existing vessels) Martin, incontrast to the present invention, discloses a side branch graftattached to the main graft as a single unit, requiring a larger profilethan the subject stent. Martin also claims and discloses much largercomponent sizes and methods for implantation (appropriate for thehypograstric artery, to which Martin is limited) than are operable insmaller vessels, such as those of the cardiac, coronary, renal,peripheral vascular, gastrointestinal, pulmonary, urinary orneurovascular system, or brain vessels. In addition, Martin requires twovascular access sites (FIG. 3, elements 16 and 18), whereas the deviceof the present invention requires only one access site, creating lesstrauma to the patient.

U.S. Pat. No. 5,643,340 to Nunokowa discloses a synthetic vascularbypass graft in which a side branch graft extends outward from the sideof a second portion of the graft unit. Nunokawa, however, disclosessurgically implanted extraluminal grafts and not intraluminal stentsdeployed by catheterization, and is therefore unrelated to the subjectof bifurcation lesions and stents, particularly stents used tointraluminally reinforce bifurcated vessels. In contrast to the presentinvention, Nunokawa is surgically implanted outside of the lumen of avessel and in fact is used to bypass damaged regions of a vesselentirely. The present invention is used to reinforce the diseasedregion, and is intraluminally implanted directly into the diseasedregion. Additionally, and unlike the present invention, the Nunokawadevice is surgically implanted and after surgical assembly of itscomponents forms a single permanently attached unit, wherein thebifurcating stent devices of the invention are deployed intraluminallyby catheter and do not require surgery or the suturing or attaching ofparts of the invention to each other or to the body vessels, allowingfor adaptation to varying branch vessel angles. Also, unlike the presentinvention, Nunokawa does not require visualization by x-ray orultrasound, as the Nunokawa device is directly seen during surgery.Lastly, the Nunokawa device cannot be deployed using catheters, is notinserted intraluminally in a compressed state and expanded while insidea vessel, and has a much larger profile than the present invention.

In general, when treating a bifurcation lesion using commerciallyavailable stents, it is important to cover the origin of the branchbecause if left uncovered, this area is prone to restenosis. In order tocover the branch origin, conventional stents inserted into the branchmust protrude into the lumen of the main artery or vessel from thebranch (which may cause thrombosis, again compromising blood flow).Another frequent complication experienced when stenting bifurcatedvessels is the narrowing or occlusion of the origin of a side branchspanned by a stent placed in the main branch. Additionally, placement ofa stent into a main vessel where the stent partially or completelyextends across the opening of a branch makes future access into suchbranch vessels difficult if not impossible. As a result, conventionalstents are often placed into the branch close to the origin, butgenerally not covering the origin of the bifurcation.

Lastly, conventional stents are difficult to visualize during and afterdeployment, and in general are not readily imaged by using low-cost andeasy methods such as x-ray or ultrasound imaging. While some prior artballoon catheters (and not stents) are “marked” at the proximal anddistal ends of the balloon with imageable patches, few stents arecurrently available which are marked with, or which are at least partlyconstructed of, a material which is imageable by currently known imagingprocedures commonly used when inserting the stents into a vessel, suchas ultrasound or x-ray imaging. The invention described in thisApplication would not work with endoscopy as currently used as animaging method due to size limitations, but future advances in limitingthe size of endoscopic imaging devices may in the future make endoscopicimaging compatible with the stents of the invention.

Accordingly, there is a need for improved stent apparatuses, mostparticularly for applications within the cardiac, coronary, renal,peripheral vascular, gastrointestinal, pulmonary, urinary andneurovascular systems and the brain which 1) completely covers thebifurcation point of bifurcation vessels; 2) may be used to treatlesions in one branch of a bifurcation while preserving access to theother branch for future treatment; 3) allows for differential sizing ofthe stents in a bifurcated stent apparatus even after the main stent isimplanted; 4) may be delivered intraluminally by catheter; 5) may beused to treat bifurcation lesions in a bifurcated vessel where thebranch vessel extends from the side of the main vessel; and 6) is markedwith, or at least partly constructed of, material which is imageable bycommonly used intraluminal catheterization visualization techniquesincluding but not limited to ultrasound or x-ray.

SUMMARY OF THE INVENTION

The present invention concerns novel stent apparatuses for use intreating lesions at or near the bifurcation point in bifurcated vessels.More particularly, the invention concerns a stent apparatus with atleast one side opening which may further comprise an extendable stentportion inserted through the side opening and at least partly inregistry with the wall of the side opening.

As used herein, the term “vessel” means tubular tissue within thecardiac, coronary, renal, peripheral vascular, gastrointestinal,pulmonary, urinary and neurovascular systems and the brain. Devicesconstructed in accordance with the invention include, singularly or incombination, a main expandable stent comprising at least onesubstantially circular side opening located between its proximal anddistal end openings, which side opening may further comprise a radiallyexpandable portion extending laterally outward from the edges of theside opening; and an expandable branch stent comprising proximal anddistal end openings and which may further comprise a contacting portionat its proximal end, and which may be constructed to form an angularlyvariable branched stent apparatus when inserted through a side openingof the main stent. The stents of the invention are marked with, or atleast partially constructed of, a material which is imageable duringintraluminal catheterization techniques, most preferably but not limitedto ultrasound and x-ray.

The stent apparatuses of the invention offers significant and noveladvantages over prior art stents in that the stents of the invention 1)can completely cover the bifurcation point of a branched vessel; 2) canaccommodate main and branch stents of differing sizes, thus providing abetter fit where the main and branch vessels are of different sizes orwhere the main and branch vessels are occluded to different degrees; 3)can fit branched vessels where the branch extends laterally from theside of the main vessel; 4) may be used to treat lesions in one branchof a bifurcation while preserving complete access to the other branchfor future treatment; 5) may be delivered intraluminally by catheter;and 6) are marked with, or at least partly constructed of, materialwhich is imageable by commonly used intraluminal catheterizationvisualization techniques including but not limited to ultrasound orx-ray, but not endoscopy.

Thus, it is an object of the present invention to provide both adouble-stent apparatus and a single-stent apparatus, each of which maybe used to cover the origin of a bifurcation in a branched vessel.

Another object of the invention is to provide a single-stent apparatuswhich may be used to treat only one branch of a bifurcation lesion whileleaving access to the second branch unobstructed.

Additionally, it is an object of the invention to provide a stentapparatus which is itself imageable by methods commonly used duringcatheterization such as x-ray or ultrasound.

Yet another object of the invention is to provide a bifurcatingdouble-stent device wherein the main stent and the branch stent orstents may be of different sizes.

Lastly, it is an important object of the invention to provide a stentapparatus which may be used to treat bifurcated vessels where the vesselbifurcation extends laterally from the side of the main vessel.

These objects and other object advantages and features of the inventionwill become better understood from the detailed description of theinvention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of the double-stent apparatus of thepresent invention in which both the main stent and the branch stent arefully dilated.

FIG. 2 is a schematic depiction of the main stent of the apparatus ofthe invention as deployed, with the side opening in registry with avessel bifurcation point.

FIG. 3 is a schematic depiction of the branch stent of the apparatus asdeployed, with the contacting portion fully expanded to contact theorigin of the bifurcated vessel.

FIG. 4 is a schematic depiction of the main stent of the apparatusdeployed within a subject vessel, after inflation of a balloon to expandthe main stent to fit the walls of the subject vessel.

FIG. 5 is a schematic depiction of the double-stent bifurcating stentapparatus, where the main stent is deployed and showing the placement ofthe branch stent apparatus prior to full deployment of the branch stent.

FIG. 6A is a schematic depiction of the stents of the invention atvarious points during deployment within a vessel. FIG. 6a depictsinitial placement of the main stent of the bifurcating stent apparatusinto the vessel, along with the insertion of a guidewire and stabilizingcatheter for placement of the branch stent into the branch vessel of thesubject.

FIG. 6b is a schematic depiction showing the main stent of the inventionexpanded by balloon expansion.

FIG. 6c is a schematic depiction of the deployment of the branch stentover the side branch guidewire, through one of the side openings in themain stent and into the branch vessel of the subject.

FIG. 6d is a schematic depiction of the removal of the protective sheathof the branch stent, allowing for full expansion of the contactingportion prior to final placement and deployment.

FIG. 6e is a schematic depiction of the compressed branch stentpositioned into the branch by the catheter with the contacting portionat least partly contacting the side opening in the main stent, but priorto full expansion of the branch stent.

FIG. 6f is a schematic depiction of the fully expanded main stent andthe fully positioned and expanded branch stent, where the branch stentis being dilated by inflation of a balloon.

FIG. 6g is a schematic depiction of the fully expanded bifurcatingdouble stent of the invention, positioned into the bifurcation point ina subject vessel.

FIG. 7 is a schematic depiction of the main stent with optionalexpandable portion, prior to balloon expansion of the expandableportion.

FIG. 8 is a schematic depiction of balloon expansion of the optionalexpandable portion of the main stent to cover a vessel bifurcationpoint.

FIG. 9 is a schematic depiction of the main stent with the optionalexpandable portion fully expanded to extend laterally from the sideopening of the main stent.

The rectilinear matrices shown in the drawings are intended to show theshapes of the surfaces only, and do not illustrate the actual surfacepatterns or appearances of the stent apparatuses of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The bifurcating double-stent apparatus 10 of the present inventioncomprises a generally cylindrical main stent 12 and a generallycylindrical branch stent 15, which are shown as fully dilated in asubject main vessel 8 and a subject branch vessel 7, as illustrated inFIG. 1.

The main stent 12 contains at least one generally circular side opening16 located between the proximal end 26 and the distal end 28 of the mainstent 12 (FIG. 2), which opening is positioned over and in registry withthe opening 48 of a branch vessel in a vessel bifurcation 50, as shownin FIG. 2. The stent 12 and the side opening are imaged during imagingprocedures either by constructing the stent of imageable materials or byplacing markers 56 at appropriate locations, such as around theperimeter of the side opening 16 in the main stent 12, and at theproximal end 26 and distal end 28 of the main stent, as illustrated inFIG. 4.

As shown in the embodiment of the invention illustrated in FIG. 4, aguidewire 20 is inserted into the vessel 8 prior to insertion of themain stent 12, and is used to guide the main stent 12 into positionwithin the vessel 8. Prior to insertion and expansion, the main stent 12is disposed around the distal end of a catheter 48 which may include aninflatable balloon 24. The main stent/catheter apparatus is thenthreaded onto the main guidewire 20 and into the vessel 8. The mainstent 12 is radially expanded by inflation of the balloon 24 until itexpands the walls of the vessel 8, and is thus affixed into place.

In a second embodiment of the invention, the branch stent apparatus 15of the present invention comprises a generally cylindrical stentcomprising a proximal end 30 and a distal end 32, as shown in FIG. 3.The proximal end 30 comprises a contacting portion, illustrated here asextended lows 18, which contacting portion, when expanded, is positionedwithin the lumen 58 of the main vessel 8 (FIG. 3) and at least partiallycontacting the perimeter of the side opening 16 of the main stent 12.FIG. 4 illustrates the positioning of the main stent 12 (withoutoptional contacting portion) in the main vessel 8 as fully expanded byinflation of the balloon 24.

As shown in the embodiments illustrated in FIGS. 4, 5 and 7, the ends ofthe main stent 12 and the expandable branch stent 15 and the contactingportion 18 are visible during insertion by placing imageable markers 56around the ends of the main 12 and branch 15 stents and the contactingportion 18 and at the proximal end 30 and distal end 32 of the branchstent. Alternatively, the stent may be at least partially constructed ofmaterial which is imageable by methods including but not limited toultrasound or x-ray imaging (but not endoscopic imaging).

As shown in yet another embodiment, the stents of the invention arecombined to form a bifurcating double stent as illustrated in FIGS. 5and 6. After insertion of the main stent as described above but prior toexpansion of the main stent (FIG. 6a), the branch stent 15 is insertedthrough a side opening 16 of the main stent 12, a guidewire 36 and astabilizing catheter 44 are inserted through the side opening 16 in themain stent 12, and into a branch vessel 7 (FIG. 6a). The stabilizingcatheter 44 is used to place the side opening 16 in the main stent 12over the bifurcation point 50 in the bifurcated vessels 7 and 8 (FIG.6a). In the embodiment depicted here, the main stent is then deployedinto position by inflation of the balloon 24 (FIG. 6b). During insertionand prior to dilation of the branch stent, the branch stent 15 isdisposed around the distal end of a branch catheter 54 which mayoptionally include an inflatable balloon 25, and the contacting portion18 of the branch stent 15 is held in a collapsed position by aprotective sheath 34, as shown in FIG. 6c.

In the bifurcating double-stent apparatus 10 of the invention, once themain stent 12 is dilated and the stabilizing catheter 44 (as shown inFIG. 6b) is removed, the branch stent 15 is inserted over the branchguidewire 36 and through the opening 16 of the main stent 12substantially as shown in FIG. 6c, and affixed in place by withdrawal ofthe protective sheath 34 (FIG. 6d) and insertion of the branch stent 15until it at least partially contacts the perimeter of the opening 16 ofthe main stent 12 by the expansion of the contacting portions 18 whichare positioned at the proximal end 30 of the expandable stent, as shownin FIG. 6e. The branch stent 15, once positioned in the branch vessel 7,may be then fully expanded by the balloon 25, as shown in FIG. 6f. Theangle at which the optionally expandable branch stent 15 is affixeddepends upon the vessel structure into which the bifurcating stentapparatus 10 is inserted. All catheters and guidewires are thenwithdrawn from the subject vessels, leaving the main stent 12 throughwhich the branch stent 15 is inserted into the branch vessel 7, forminga bifurcated stent 10 (FIG. 6g).

In the embodiment shown in FIGS. 7-9, the main stent 40 with expandableportion 38 is positioned within the vessel 8 by the guidewires 20 (FIG.7), and affixed in place by radial expansion of the main stent 40, mostparticularly by inflation of the balloon 25 (FIG. 8). The main stent ispositioned so that the opening 16 is directly over the bifurcation point50 in the subject vessels 7 and 8 (FIGS. 7 and 8). In order to aid suchpositioning, a side branch guidewire 36 and a stabilizing catheter 44(as depicted in FIG. 7) are also inserted through the opening 16 of themain stent 40 and through the expandable portion 38 and into the branchvessel 7 (FIG. 8). Optional expandable portion 38 is initially alignedwith the cylindrical wall of stent 40, prior to radially outwardexpansion of expandable portion 38.

The optional expandable portion 38 of the main stent 40 is then expandedradially and in an at least partially perpendicular manner to the sidesof the main stent side opening 16 (FIG. 8). In the embodimentillustrated in FIGS. 7 and 8, a balloon 25 is deployed along the sidebranch guidewire 36 through the expandable portion 38, and inflateduntil the expandable portion is fully expanded into the branch vessel 7to cover the bifurcation point 50 of the branched vessel, as illustratedin FIG. 8. In order to extend the expandable portion 38 into the branchvessel 7, a balloon 25 disposed around a branch catheter 54 which isthreaded along the side branch guidewire 36, through the main stent 40,through the opening 16 and expandable portion 38, and into the subjectbranch vessel 7 as shown in FIG. 8. The expandable portion 38 is thenextended into the branch vessel 7 by inflation of the balloon 25, whichpushes the expandable portion 38 outward radially and lateral to theside opening, into the branch vessel 7 (FIG. 8). Once all catheters andballoons are withdrawn, the expandable portion 38 is arrayed in lateralorientation to the sides of the opening 16 in the main stent 40, andsurrounding the opening 16 into the vessel branch (FIG. 9). Theguidewires 20 and 36 are then withdrawn from the main and branchvessels.

In the double stent apparatus of FIG. 5 and in the main stent withexpandable portion illustrated in FIGS. 7 and 9, the main stent as wellas the expandable portions may be constructed at least partially ofimageable material or marked with imageable markers 56 at suitablelocations, including around the perimeter of the side openings of themain stent and at the ends of the expandable portions.

When reinforcing a bifurcated vessel where both branches of the vesselrequire reinforcing, either 1) the single main stent with the expandableportion is used whereby the expandable portion extends into the vesselbranch at least partly covering the origin of the bifurcation, which maybe used alone or in combination with any conventional stent; or 2) themain stent without the expandable portion and at least one branch stentwith contacting portion are used, the branch stent placed to extendthrough at least one side opening of the main stent into at least onebranch vessel, wherein the branch stent is at least partially inregistry and contacting the edge of the side opening through which itextends. The branch stent extends laterally at varying angles to theside opening of the main stent. When treating a bifurcated vessel wherethe area to be treated spans the bifurcation and unobstructed access tothe unstented vessel is required, the main stent may be used either withor without the expandable portion, wherein at least one side opening isplaced over the bifurcation point.

The stent apparatus of the invention may be constructed from anynon-immunoreactive material, including but not limited to any of thematerials disclosed in the prior art stents which are incorporatedherein by reference. It is intended that the stent apparatuses of theinvention may further be at least partially constructed of, or marked atcertain points with, a material which may be imaged, most particularlybut not limited to by x-ray and ultrasound.

The stents of the invention may be deployed according to known methodsutilizing guidewires and catheters, which are then withdrawn from thesubject following deployment of the stents. The subject stents may beself-expanding to conform to the shape of the vessel in which they aredeployed, or they may be expanded utilizing balloon catheters, or by anyother method currently known or developed in the future which iseffective for expanding the stents of the invention. It is contemplatedthat prior to deployment the stents will be in a collapsed state, andwill require either mechanical expansion (such as, for example, byballoon expansion) upon deployment or, for self-expanding stents, willrequire that the stent be confined to the catheter until deployment by,for instance, a retractable sheath, in which the sheath is removedduring deployment and the stent self-dilated. The stents of theinvention and the optional expandable portion of the main stent of theinvention expand radially from their longitudinal axis, lateral to theside opening of the main stent. Other methods of dilation of the stentsof the invention may exist, or may become available in the future, andsuch methods are contemplated as being within the scope of thisinvention.

It is intended that the invention include all modifications andalterations from the disclosed embodiments that fall within the scope ofthe claims of the invention.

We claim:
 1. A method of positioning a main stent comprising a stentbody having a side hole at a vessel bifurcation, said method comprising:positioning the main stent within a main vessel at the bifurcation sothat the side hole is aligned with an ostium of a branch vessel, whereinthe side hole comprises an opening surrounded by an expandable portionthat is integrally formed with the stent body, wherein the expandableportion is flush with the stent body during positioning of the mainstent within the main vessel; expanding the main stent within the mainvessel; and expanding the expandable portion of the side hole byinflating a balloon which extends through the side hole into the branchvessel, wherein expanding the expandable portion further comprisesexpanding the expandable portion radially and in at least a partiallyperpendicular manner relative to the stent body so as to extend into thebranch vessel.
 2. A method as in claim 1, wherein positioning comprisesinserting a stabilizing catheter over a side branch guidewire throughthe side hole and into the branch vessel.
 3. A method as in claim 2,wherein expanding the expandable portion of the side hole comprisesremoving the stabilizing catheter from over the side branch guidewire,advancing a balloon catheter over the side branch catheter so that theballoon thereon is positioned within the side hole, and expanding theballoon on the balloon catheter within the side hole.